The present invention relates generally to metal working tools. More particularly, the present invention relates to punch assemblies used in punch presses.
Sheet metal may be economically fabricated into a wider range of useful products including chassis for appliances and electrical devices. Turret-type punch presses have found wide use in fabricating sheet metal. Turret-type punch presses employ an upper, generally cylindrical turret which holds a series of punch tools spaced circumferentially around its periphery, and a second, lower turret holding a series of dies circumferentially spaced about that turret""s periphery, each turret being rotatable about a vertical axis to bring an appropriate punch and die pair into vertical alignment at a work station. By appropriately rotating the two turrets, an operator can bring a number of punches and dies sequentially into alignment at the work station to perform a series of sequential and different punching operations on a work piece.
Repeated use of a punch assembly in a punch press operation results in the natural dulling and wear of the punch tip. Once the tip has become dull, the effectiveness of the punch assembly is reduced and the punch tip must be sharpened. Sharpening may be accomplished by grinding the end of the punch tip, and this results in shortening the length of the punch. The length of the punch may then be adjusted to compensate for the ground-off portion.
The longitudinal axis of the punch assembly is typically placed in coaxial alignment with the axis of the ram. The ram of the punch press then strikes the punch with great force on it""s impact surface.
The present invention relates generally to metal working tools. More particularly, the present invention relates to punch assemblies used in punch presses. An adjustable length punch assembly in accordance with the present invention may be used with a punch press including a tool holder adapted to receive the punch assembly and a ram adapted to move longitudinally along a ram axis. An adjustable length punch assembly in accordance with the present invention advantageously includes a punch body assembly disposed in threading engagement with a drive body assembly having a surface adapted to be struck by the ram of the punch press. The length of the punch assembly may be adjusted by the rotating of one body relative to the other body. The adjustable length punch assembly advantageously includes a lock mechanism for selectively preventing rotation of the punch body assembly relative to the drive body assembly. The lock mechanism advantageously features a lock shaft coupled to one of the bodies and a lock key slidingly coupled to the other of the bodies such that the lock key slides along a lock key path. The lock key path is advantageously disposed at an angle relative to the ram axis when the punch assembly is received by the tool holder.
In one implementation, the adjustable length punch assembly features a lock mechanism having a lock shaft coupled to one of the bodies and a lock key slidingly coupled to the other of the bodies such that the lock key slides along a lock key path. The lock key path may be advantageously disposed at an angle relative to a longitudinal axis of the punch assembly. When the punch assembly is received by the tool holder of a punch press, the lock key path is advantageously disposed at an angle relative to the ram axis of the punch press.
In some implementations of the present invention, the angle between the lock key path and the longitudinal axis of the punch body assembly is a right angle. In other implementations, the angle between the lock key path and the longitudinal axis of the punch body assembly is an acute angle. In some implantations, the lock key path is generally parallel to the striking surface of the drive body assembly.
In one aspect of the present invention, the lock key is moveable between a first position in which the lock key engages the lock shaft and a second position in which the lock key disengages the lock shaft. The adjustable length punch assembly may advantageously include a means for biasing the key toward the first position. In one implementation of the present invention, the means for biasing the key toward the first position comprises a spring having a first end seated against the lock key and a second end seated against one of the bodies.
In one aspect of the present invention, the lock shaft has a first axial degree of freedom relative to the lock key. In an advantageous implementation of the present invention, the first axial degree of freedom is generally parallel to the longitudinal axis of the punch assembly.
In one implementation of the present invention, the lock key includes an opening adapted to receive the lock shaft. The opening may be defined in part by a shaft engaging portion of the lock key. In some embodiments, the shaft engaging portion of the lock key advantageously includes at least one tooth. In other embodiments, the shaft engaging portion of the lock key advantageously includes at least one flat.